The invention relates to a mechanism for winding a ribbon on a spool, and more particularly, to a mechanism for effecting a constant ribbon winding rate although the diameter of the spool increases as the ribbon is wound thereon.
It is important that the winding rate of a ribbon upon a spool remain constant as the diameter of the spool increases with the ribbon being wound thereon. Such mechanisms are needed, for instance, in office machines for the transport of carbon ribbons or correction ribbons. In order to realize the optimum utilization of such ribbons, impressions which are made upon the ribbons must be closely and uniformly spaced. The impressions must not intersect one another, and the spacing between the impressions must not increase as the diameter of the ribbon which is wound upon a take-up spool increases. One mechanism for the transport of a take-up spool employs the use of wrap springs and is shown in German Disclosure No. DT-OS 23 37 191. The patent to Hengelhaupt, U.S. Pat. No. 3,923,141, discloses a mechanism for providing a constant feed rate increment for a ribbon. In this assembly, a transport roller drives the periphery of a flange on a ribbon take-up spool, and means are provided for decreasing the angle of rotation of the transport roller as the diameter of the wound ribbon on the take-up spool increases.